This article describes our experience lengthening limbs in 156 patients by the method of Bliskunov's. Subfascial control pressure with a "Stryker Intra-Compartmental Pressure Monitor", according to standard procedure Whitesid's,Noted that where lengthening segments (femur, tibia) at the standard speed of 1 mm / day, podfastsialnoe pressure does not exceed the normal version (20 mm Hg. Hg.). In the two cases where the extension was carried out with the excess of this rate - there is an increase subfascial pressure with the development of the classical clinical symptoms MHIS. Described in detail these two observations at a deviation from the norm.Microcirculation disturbance induced by MHIS, the cause of which is to increase the elongation rate of the segment can lead to complications such as delayed fusion, pseudoarthrosis, inflammation of soft tissue and osteomyelitis. MHIS prevention in this case serves as a compliance rate of elongation of no more than 1 mm / day.

1. Introduction
In works of G.A. Ilizarov (1968), V.I. Stetsuly and V.V. Veklicha (2003), A.I. Bliskunov (1983) and others devoted to distraction osteosynthesis it was defined the rule of optimal daily distraction of long bones – 1 mm.
The velocity of distraction is not limited by the ability of the distraction device (external or internal) to conduct diastasis between the fragments per unit of time (usually taken daily), but by creation of optimal conditions for the possibility of extension. Modern distraction devices allow extension with significant, almost unlimited speed, the minimum elongation step can reach a 1/100 of a millimeter. Speed of distraction is limited by muscles – inertial system that enables the elongation of up to 20% of the original length of the segment. Subsequently, elastic elongation and regeneration of bone at the point of distraction will be stopped almost completely and intensification of distraction will increase time required for “maturation of the regenerate,” until exhaustion of the bone regenerative capacity (Klimovitsky et al. 2009). Also, if elongation speed is ungrounded high there is a risk of local hypertensive ischemic syndrome (LHIS), and this risk increases significantly in patients with fibrotic changes of extendible segment that were previously obtained due to trauma, surgery or extension of a segment by more than 20% of the initial length. LHIS developing on the background of distraction causes a violation of the tissues nutrition, neuritis development, scar-fibrotic degeneration of muscles and fascia, which leads to secondary changes and forms a closed “vicious circle” – a sharp decrease in elasticity, increases the resistance of the tissues to distraction, makes overload on distraction devices, reduces elongation rate. Further the reparative regeneration of whole segment is decreased – from the formation of the bone regenerate in slow time, to generation of defective bone remodeling, unable to bear the functional load. In rare, severe cases, the regeneration process stops, and persistent pain syndrome appears while attempting to carry out extension (Klimovitsky et al. 2009; Klimovitsky 2010; Dragan V et al. 2011; Dragan V et al. 2011).
Distraction forces and the resistance of the soft tissues during elongation are antagonistic. Moreover, there are differences in the correlation of action of these antagonist forces for elongation when using external and internal devices. In particular, V.G. Klimovitsky, V.V. Dragan, L.E. Goncharova et al (2010) described this system, in comparison with the movement on the road: when we use intraosseous methods – the force vectors are passing one another “on contrary roads with dividing strip”, which serves the cortex of the bone; and if we use external methods – one of the forces moves “against the rules on the one-way road” (Klimovitsky et al. 2009).

2. Material and methods
We have performed elongation of the lower limbs with the help of intraosseous devices in 156 patients:
– Monosegmental – 87 cases:
• 86 – thigh (average elongation 8,3 ± 0,5 cm);
• 1 – shin (5 cm);
– Pair – 64 patients:
• 55 – thigh (average elongation 8,5 ± 0,5 cm);
• 9 – shin (average elongation value 4,5 ± 0,3 cm);
– Multipair elongation – 4 patients;
• One patient underwent simultaneous lengthening of the four segments;
• Three patients, “two by two” with average elongation – 12,5 ± 0,5 cm. We should note one patient in this group, to whom it was performed simultaneously both thigh (7.5 cm) and shin extension (5 cm), and in second stage – lengthening of shin (4 cm). The total amount of elongation was 16.5 cm.
Being inside the bone (femur or tibia), drive intraosseous device performs the function of bone fragments holder and shock absorber of power loads on the bone. Distraction mechanism is working due to tripping unit carried by the actuator fixed to the outer body of device, and a special spring-ratchet mechanism, which is located inside the outer body of device. The presence of teeth in the ratchet mechanism make possible to carry out distraction with minor amplitude of movements of the actuator, which patients make on their own, consistently carrying out strictly metered and smooth dynamic extension of a rod system, thereby increasing the diastasis between extendible fragments of the segment (Klimovitsky et al. 2009; Klimovitsky 2010; Dragan V et al. 2011; Dragan V et al. 2011).
After completion of the distraction program and achievement of the desired value of bone lengthening, we disable drive of distraction apparatus that connects the outer body of device with the iliac crest. The unit is removed from the bone after a full functional rehabilitation and reconstruction of distraction regenerate into a regular bone.
Elongation programs aimed at maximum result when simultaneous or subsequent distraction of respective pairs of segments is performed can be called an appropriate term “multipair elongation” ie elongation pair by pair. The prefix indicating the plurality is selected as “multi”, that means a plurality with homogeneity sense (Klimovitsky et al. 2009; Klimovitsky 2010; Dragan V et al. 2011; Dragan V et al. 2011).
Elongation program selection depends on:
1. specific clinical aim;
2. patient health status;
3. presence of post-traumatic changes, including scar-fibrotic degeneration;
4. constitutional features and the level of preparation for the distraction process;
5. consideration of the interests and wishes of the patient.
Nevertheless, it is necessary to specify the optimal values of elongation which are serving as primary indicative points for planning of any particular program of elongation. The term “optimal” in this case means such distraction algorithm where elongation occurs in sufficiently comfortable conditions for the patient, without significant stress to the organism, muscle-ligament system, joints, without risk of local hypertensive ischemic syndrome, with good results of recovery of the lower extremity function, including the time indices (Klimovitsky et al. 2009; Klimovitsky 2010; Dragan V et al. 2011; Dragan V et al. 2011).
The elongation plan includes the schedule of distraction until achievement of the planned extension of the segment, and also daily plan with calculation of distraction step and taking into account planned pauses for the adaptation of muscles to stretch as well. When multifractional mode of distraction is used the risk of LHIS development is significantly reduced.
When planning monosegmental and pair elongation of thigh it is important to consider that after distraction to 4.0 – 4.5 cm, the elastic properties of muscles begin to decrease markedly, and gradually increases resistance in response to a distraction that results in a relative reduction of the muscle sheaths volume and gives the start for LHIS.
It should also be noted that the program of multipair extension “two by two” is more favorable for joints. Especially it is necessary to highlight the situation with the knees when the load on the articular apparatus is largely determined by the combined opposition of individual intersegmental muscle groups, as well as the stresses of the adjacent segments, in response to distraction. Knee joints are located in a kind of “lock”. Therefore, time diversity of peak loads on the joints is an important moment in organization of proper rehabilitation. This definition applies also to tension of muscle sheaths – in case of rapid distraction decrease of sheaths volume occurs, which leads to the development of LHIS. Unlike muscles sheaths are not elastic, for their lengthening we need a certain amount of time, which only occurs when slow multifractional distraction is used (Klimovitsky et al. 2009; Klimovitsky 2010; Dragan V et al. 2011; Dragan V et al. 2011; Strafun et al. 2009; Tkach 2012).
It is also important to note that the method of bone lengthening with the help of intraosseous devices makes it possible for patient and doctor to begin active rehabilitation measures earlier, which allows joints to overcome distraction stress loads more easily.
It should be noted that the above mentioned programs are optimal for most patients. Based on the obtained clinical experience, they can be recommended as basic for drawing elongation programs. However, taking into account the individual characteristics of the specific patient, adequate adjustments in the planning and in the implementation of the program of distraction should be made.
Sometimes, we had to retreat from the previously mentioned “classical” speed of distraction. In some cases, this deviation had objective reasons – on the control radiograph performed during distraction, formation of the regenerate in an uncharacteristically early period of distraction process was noted. The average rate of distraction of 1 mm/day was insufficient to carry out the planned program of distraction, because of the threat of accelerated formation of the regenerate and the onset of the early “fusion” of fragments of the femur (we observed one such patient who carried elongation of both thighs). In other cases, speed of distraction was changed by patients who want to “accelerate the time of treatment.” Typically, patients make distraction on their own, outpatient, and their actions were motivated primarily by the following: “the device worked by itself, without my participation”.
The increase in speed of distraction is usually accompanied by its characteristic set of negative symptoms: hyperextension of fascial sheath, with the creation of conditions for development of LHIS, the formation of contractures of adjacent joints, slowing formation of the regenerate in distraction zone, excessive stress on the distraction devices which leads to damage of blacket, migration of screws and break of ratchet.
The observation group of changes of intracompartmental pressure dynamics during lengthening of lower extremity segments included 5 patients who underwent lengthening with fully implantable guided intraosseous devices. Intracompartmental pressure measurement according to the classical standard method Whiteside, using a serial device “Stryker Intra-Compartmental Pressure Monitor”, using a single set of interchangeable needles, syringes and membranes for simultaneous determination of indicators. Shin was lengthened in one case, in four cases there was lengthening of the thigh; and of these, in two patients it was performed “the pair” extension. Thus, we controlled intracompartmental pressure during distraction of 7 segments. In three cases, there was an increase in speed of distraction, in 4 cases distraction took place in the normal mode, with a speed of 1 mm/day. With the standard velocity of elongation, the value of intracompartmental pressure did not change. Quite different clinical picture was observed in case of deviation from “gold standard of extension”.

3. Results
Following observations may serve as an illustration.
Patient O., 47 years old, which was carried out an elongation of both thighs with a cosmetic purpose. The program has been drawn up for the elongation of both thighs for 7 cm. Patient was inspected before surgical treatment (Fig. 1) and extra – CT scan was made to determine the exact length of the segments of the lower extremities.

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Figure 1. Radiographs of a patient O., 47 years in the AP (a) and lateral (b) projections before elongation.

Surgical interventions – subtrochanteric osteotomy of the left femur, implantation of intraosseous distractor, originally was produced on the left thigh and in 10 days – on the right. Distraction initiated 10 days after implantation of distractors with standard elongation speed of 1 mm/day. Used distraction device allows performing a multifractional distraction. In 1 step of distractor (1 cycle of the ratchet-gear) occurs extension of the rod on the length equal to 1/21 mm. Thus, it is possible to perform the daily program extension in 4–7 stages. On the control radiograph after 20 days, a 10 mm distraction was noted, with the presence of radiographic evidence of the formation of the bone regenerate (Fig. 2).

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Fig.2. Radiographs of a patient O., 47 years in the AP (a) and lateral (b) projections, 20 days after beginning of distraction

In 30 days, significant ossification centers in the distraction regenerate were observed (Fig. 3). Distraction on the left femur was impossible – distractor did not work. An additional surgery was performed – reinstalling of the distraction device and osteotomy of bone regenerate.

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Fig. 3. Radiographs of a patient O., 47 years in the AP (a) and lateral (b) projections, 30 days after beginning of distraction

Distraction was started on the 5th day. To prevent premature “regenerate union” distraction speed was

increased in 1,5–2 times on both femurs, and brought up to 2–3 mm/day. Each time when the distractor mechanism is working the patient feels a “click”, which is useful for calculating the value of distraction. After the completion of the plan of elongation 3-dimensional computed tomography was performed to determine the length and equality of extensible segments (Fig. 4).

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Fig. 4. CT scan of patient O., 47 years. Allows to specify the length of the extension, equality of segments and the quality of the bone regenerate

The program of distraction is completed, the intraosseous devices are disabled. Control radiographs are made in 8 months after surgery (Fig. 5).

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Fig. 5. Radiographs of patient O., 47 years old, right femur (a) and left femur (b) after completion of distraction

Intracompartmental pressure in this patient was monitored at various stages of treatment. Initially, prior to surgery, on the left and right thighs it was the same – 7 mm Hg in the front thigh sheath and 5 mm Hg in the back thigh sheath. Second time the intracompartmental pressure was monitored when a distraction of 30 mm was reached. In our case, this period coincided with the violation of the distractor on the left thigh, which is why the patient stopped distraction on both thighs. Intracompartmental pressure was: on left thigh – 7 mm Hg in the front thigh sheath and 7 mm Hg in the back thigh sheath; on right thigh – 8 mm Hg in the front thigh sheath and 7 mm Hg in the back thigh sheath.¬¬ When extending the thighs, with the speed that almost two to three times higher than the recommended one (1 mm/day), after reaching 70 mm distraction, before disconnecting distraction mechanism intracompartmental pressure was monitored. Tissue pressure had the following characteristics: right thigh – front sheath 17 mm Hg and back sheath 18 mm Hg; left thigh – front sheath 19 mm Hg and back sheath 19 mm Hg. Taking into account increased velocity of distraction and increased intracompartmental pressure, a moderate pain syndrome appeared in the lower extremities, estimated by the patient on a visual analogue scale (VAS) to 5 points. It should be noted that during period of 1 mm/day distraction there was no pain in lower extremities and it was relieved on the 3-rd day after cessation of distraction.
On the control examination in 8 months after implantation of distractor devices, tissue pressure was determined on the same level as before surgery, it was the equal to the 7 mm Hg in the front and rear sheaths of both thighs. Assessment of pain syndrome on the VAS was equal to 0 points.
This clinical case is a good example that an “abrupt” extension of a segment, which occurs during planned distraction or in case of treatment of fractures with extension method, establishes all conditions for the development of LHIS (Strafun et al. 2007; Tkach 2012). This syndrome can pass in “silence” under the guise of pain syndrome of the acute phase, but result in consequences in residual period – such as formation of false joints, delayed union or nonunion, which in case of osteosyntesis will be accompanied by break of metal fixation device. The next negative consequences of LHIS are dysfunction of the motion in adjacent joints, decrease of muscle power in segment and neurological symptoms manifestation due to form of scar-fibrous degeneration of soft tissues as a result of acute ischemia (Strafun et al. 2007; Strafun et al. 2009;Tkach 2012).
In the second clinical observation, in contrast to the first, where we were consciously forced to increase the velocity of extension, distraction speed was increased by patient himself.
We conducted lengthening of the femur in patient G. 30 years old, with post-traumatic shortening of the right thigh by 4 cm. He was treated after fracture of the femur by skeletal traction with delayed union. In the following, a surgery was performed – open reduction, osteosynthesis of femur with plate (Fig. 6).

During the treatment, there was severe varus deformity of the femur. The consolidation of the fracture occurred, and metal plate was removed and 5 years after injury patient returned to our hospital. The examination revealed post-traumatic varus deformity of the thigh, with the presence of anatomical femoral shortening by 4 cm (Fig. 7).

Fig. 7. CT scan of patient G., 30 years old, before elongation

In this patient a surgical intervention was performed – corrective subtrochanteric osteotomy and intramedullary distractor implantation into the right femur. Wounds have healed by first intention. On the 10-th day distraction was started, with recommended speed of elongation of 1 mm/day (Fig. 8).

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Fig. 8. Radiograph of patient G., 30 years in the AP (a) and lateral (b) projections, after beginning of distraction

In 2 weeks after surgery, during the examination, patient complained of pain that was evaluated on VAS up to 7 points, on the control X-ray distraction gap was 27 mm. The patient was given a talk about the need to comply with the prescribed treatment, orthopedic regimen and elongation speed. Intracompartmental pressure, compared with the contralateral side was increased up to 23 mm Hg in the front sheath and 25 mm Hg in the rear sheath, while intracompartmental pressure in the left thigh (non-operated) in the front and rear sheathes were similar, and corresponded to 4 mm Hg. Clinically there were defined pain in the right thigh, mostly along the sciatic nerve and pain in the right knee joint. A conservative therapy (vascular, anti-inflammatory, neurotrophic) was prescribed and distraction was terminated. After 10 days clinical symptoms of muscle tension were absent, pain syndrome was ceased; control of intracompartmental pressure – in both sheathes was 7 mm Hg. Distraction with speed of 0.5 mm/day was restarted (Fig. 9).

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Fig. 9. Radiographs of patient G., 30 years in the AP (a) and lateral (b) projections on the 24-th day after beginning of distraction
After distraction reached 40 mm, the program of extension was completed.

4. Discussion
Basing on the mentioned above we can conclude that:
On the beginning of distraction – in the first 2 weeks of lengthening recommended limit of distraction speed is 0.5–0.8 mm per day, with a consequent increase in the daily velocity of distraction to the level necessary for achievement of the planned aim. In the second phase of the extension program that begins with a mark of 4 cm, it is recommended to make a daily speed of elongation of 1 mm/day, with obligatory pauses (stops in distraction) in the extension to provide a more comfortable and safe distraction process for the patient.
In case of patient compliance with the recommended speed of elongation of a segment intracompartmental pressure does not exceed the threshold value of 15 mm Hg.
If speed of bone elongation exceeds recommended levels it will increase intracompartmental pressure with the threat of development of chronic local hypertensive ischemic syndrome.